Method of recovering hydrocarbon



Dem 14, 1937 P. M, RAIGORODSKY METHOD OF RECOVERING HYDROGARBON VAPQRS Original Filed Dec. 29, 1950 W E mfi M NM 0 w/ w mw J QM |L 1.

Reissued Dec. 14, 1937 UNITED STATES METHOD OF RECOVERING HYDROCARBON VAPORS Paul M. Raigorodsky,

Petroleum Engineering,

Tulsa, Okla, assignor to Inc., Tulsa, Okla., a

corporation of Delaware Original No. 1,977,087,

dated October 16, 1934,

Serial No. 505,381, December 29, 1930. Ap-

plication for reissue rial No. 100,286

7 Claims.

My invention relates to a method of recovering vapors from pressure distillate, or any other product derived from cracking or topping of crude petroleum and its by-products, and com- -.5 prising a series of hydrocarbons and accompanying vapors.

In methods formerly employed such vapors were recovered toa large extent by several stages of compressions; coolers, condensers and separators being used between the various stages.

The principal objection to this method, however, was the remaining high content of usable hydrocarbons in the residue gas, and the vapors thus derived and condensed were not sufilciently controlled as to their composition, recovery, gravity, etc.

In later practice an absorption type of plant was designed for recovering the greater percentage of the vapors in a more economical manner.

This type of plant, wherein the absorber contains a plurality of trays, of which the bubble type is most common, is used for absorbing the desirable gasoline and lighter fractions of petroleum in a heavier oil, the combined oil being delivered to a still. The vapors freed in the still are conducted therefrom through fractionating equipment for removing the entrained oil and for dividing the vapors into desired fractions which are finally condensed.

Although this method is a great improvement over the former method the installation and operating costs of the absorption type of plant is comparatively great, andundesirable or uncontrolled amounts of propane and butane or other hydrocarbons remain in the final product. In later equipment stabilizers or rectifiers were added to remove the undesirable light ends after the product had been passed through the fractionating equipment.

The principal objects of my invention are to further decrease the installation and operating costs of plants for the recovery of desirable hydrocarbons from refinery vapors and to control the recovery of the volatile products such as propane and butane, thereby producing a more stable and controlled product not subject, to such a great degree, to evaporation and weathering.

In accomplishing these and other objects of my invention I have provided an arrangement of apparatus wherein the absorption plant is entirely September 11, 1936, Se-

eliminated and wherein the vapors, heated by compression, are conducted at high pressures directly to a rectifier without cooling, or condensing, or separation.

The arrangement of the apparatus is illustrated in the accompanying diagrammatical drawing or flow sheet of the plant.

The apparatus may for convenience be divided into four units as follows:

(A) The debutanizer wherein butane and propane are separated from pressure distillate or other charging stock.

(B) The low pressure compressor for taking uncondensed vapors from the debutanizer and preferably mingling them with tail gases from crude distillation streams and vapors from storage tanks and loading racks.

(C) The high pressure compressor whereby vapors passing through unit B are delivered to the stabilizing rectifier.

(D) The rectifier wherein hot vapors from unit A are stabilized, either alone or with distillate from units A and B.

In practicing my improved method with the apparatus illustrated in the drawing, and by particular reference to treatment of pressure distillate of crude oil from the Mid-Continent field, I designates a run down storage tank for receiving pressure distillate at about 20 poundsgauge pressure through a line 2 from a source of supply, such as a cracking still (not shown).

From the storage tank the liquid distillate is drawn through a line 3 by a pump 4 and delivered through a line 5, heat exchanger 6, line 8 and preheater 1 into a debutanizer 9 at pressure ranging from thirty to seventy-five pounds and temperature of approximately 150 F., according to the product desired.

The debutanizing column is preferably of tray type, as indicated at ill, for efiecting fractional distillation of liquid and vapors, although sharp cuts are not obtained either in the bottom or top products, the bottom products, however, being substantially stable. Liquid drawn from the bottom of the stabilizing column is passed by a line l2 through a kettle or reboiler H where it is heated to approximately 300 F. at a pressure of about thirty pounds, through the heat exchanger 6, connecting line 13 and cooler M to storage outside the system here involved.

Bottom product of the debutanizer for a charging stock of the character stated selected for example may consist of the following combination:

Liquid volume percent R Methane Ethane Propane Butanes Pentanes Hexanes and heavier M01. percent The debutanizer bottoms have-an- En'gler distillation as follows:

The overhead product, including light ends of vapors returned to the column from the reboiler, are led oiT by line |5 through a cooler l6 and pass through a line. I! to a separator l8 at about 80 F. A limited quantity of condensate is drawn from theseparator l8 to the debutanizer colunm for reflux and the balance conducted to mixing tanks in the stabilizer unit.

If the debutanizer is operated at pressures less than twenty, pounds, vapors uncondensed from the separator I8 are drawn through a line 2| and scrubber22 into a single stage compressor 23. If the debutanizer is operating-at pressures over twenty pounds the uncondensed gases from separator l6 may. be led through a scrubber 25 to the high pressure compressor 26 for direct delivery to the stabilizing column. Vapors drawn from outside the debutanizing system enter the system through lines 21 and 28 to unite with vapors drawn from separator IE to pass therewith through the scrubber 22into compressor 23.

()utside vapors may be supplied to the storage tank through the high pressure compressor and its scrubber by lines 29 and 30. Condensate in the scrubberZZ of the low pressure unit is drawn ofi? to the storage tank through line 42.

Vapors, leaving the compressor 23 at a pressure of about forty-five pounds, are passed through a cooler-32 into an accumulator tower 34 where a further separation takes place, condensate passing from the lower portion of the tower 34 through line 35 to mixing tank 20. Va-- pors uncondensed in the tower, pass through line 36 to the scrubber 25 of the high compression unit, and condensate of said vapors, with that of other vapors entering the scrubber, pass to the mixing tank. Vapors uncondensed in the scrubber 25 are drawn into the low pressure cylinder of compressor 26 through a line 31 and pass from the low pressure cylinder through a line38, cooler 39 and line 40 into an accumulator 4|, where further separation takes place, condensate passing from the accumulator through line 35 at a pressure of approximately eighty pounds to the mixing tank 20.

Vapors uncondensed in the accumulator 4| .are

of the compressor 26 and inder,

delivered from said cylat a pressure of approximately three hundred pounds, through a line into the stabilizing rectifier column 46, preferably at spaced points indicated drawn from the at 41, together with condensate mixing tank 20 through a line 48 by a pump 49 and by the pump delivered through line 50, heat exchanger 5| and preheater 52 to join vapors delivered through-line-AE for inlet to the column- 46 10 at the points 41.

The rectifier 46 is of bubble plate type, including a sufficient number of fractionating trays to effect close frac propane and lighter hydrocarbons with a variable tionation to a top separation of amount of butane according to the bottom prodnot desired. The lower fractions collecting at the bottom of'the' rectifier are removed through a reboiler 54, and in divided flow through line 55 and: through shunt line 56 and heat exchanger 20 cooler 58 to a temperary storage tank 59,cr directly through a line 60 to a treating plant (not shown) The commingled vapors from, tl-1eccompresso1' and mixing tank enter the rectifier at a temperature or" from 180 to 200 F.

The overhead the rectifier through line 62, cooler 6| line 63 to a separator 64.

are drawn from drygas for fuel, and liquid. condensate pumped 25 product passes from the top of and the Non-condensible gases the separator through line 66 as 30 from the separator through line fifi atea-tem- 'perature of about 75 column.

Feed to the debutanizer and rectifiercolumns iscontrolled by volume controllers and 1 regulatorslator 34and in in the reboilers trolled by F. for reflux in the rectifier rectifier and reflux to both the 35 6'; in the respective lines, provided for maintaining in the vapor separators, the

66 are the mixing tank. Temperatures ill and 54 are automaticallyconregulators 6 9.

' The stabilized product from the rectifier, when containing-about eighty percent of the available butaneavaiiable in the combined feed to the column, has the following characteristics:

Pentane Hexane Percent 5 If desired, the recovery of the butane may be increased to something over ninety per cent.

From the fore method desirable high bo' cracking stills and casing sources, usually processes, may

use either alone or by blending with other hydrocarbon products and that in effecting separation of the vapors heat generated 7 advantage is taken of the by compression to effect saving in operating costs.

What I claim Patent is:

and desire to secure by Letters 1. 'I'hemethod of stabilizing petroleum oil pressure distillate and recovering desired light comseparating said into a heavy sta tion containing ponents thereof which comprises, heating and distillate in a rectification. zone bilized fraction and a light fracthe desired light components as vapors and undesirable gaseous components, separately removin subjecting the li g the fractions from saidzone, ght fraction to condensation. and

separating condensate from remaining vapors and gases, subjecting said remaining vapors and gases to compression and cooling in a plurality of stages at progressively increasing pressures with separation of condensate from uncondensed vapors and gases after each stage, collecting and mixing together all the condensates, introducing the mixed condensates and said uncondensed vapors and gases into a second rectification zone and rectifying the materials therein into a stabilized light fraction of pressure distillate which is withdrawn in liquid form from the bottom of said zone, and withdrawing gaseous constituents from the top thereof.

2. The method of recovering desirable hydrocarbons from an original normally gaseous charge consisting mainly of normally gaseous constituents and containing said desirable hydrocarbons which consists in subjecting said charge to com pression and cooling in a plurality of stages at progressively increasing pressures with separation of condensates from uncondensed portions of the charge after each of said stages except the final one, introducing the portion of the charge leaving the final stage of compression directly into a rectification zone, mixing said condensates and introducing the resulting mixture into said rectification zone, therein rectifying all of these materials into a stabilized fraction containing said desirable hydrocarbons which is withdrawn from the bottom of said zone and withdrawing the remainder of said charge from the top thereof.

3. The method of recovering. desirable hydrocarbons from an original normally gaseous charge consisting mainly of normally gaseous constituents and containing said desirable hydrocarbons which consists in subjecting said charge to com pression and cooling in a plurality of stages at progressively increasing pressures with separation of condensates from uncondensed portions of the charge after each of said stages except the final one, introducing the portion of the charge leaving the final stage of compression directly and without cooling into a rectification zone, mixing said condensates and introducing the resulting mixture into said rectification zone, therein rectifying all of these materials into a stabilized fraction containing said desirable hydrocarbons which is withdrawn from the bottom of said zone and withdrawing the remainder of said charge from the top thereof.

4. The method of recovering desirable hydrocarbons from an original normally gaseous charge consisting mainly of normally gaseous constituents and containing said desirable hydrocarbons which consists in subjecting said charge to com pression and cooling in a plurality of stages at progressively increasing pressures with separation of condensates from uncondensed portions of the charge after each stage, collecting and mixing together all the condensates, heating the mixed condensates, introducing the mixed and heated condensates and said uncondensed portion of the charge into a rectification zone, therein rectifying these materials into a stabilized carbons from an original normally gaseous charge fraction containing said desirable hydrocarbons which is withdrawn from the bottom of said zone and withdrawing the remainder of said charge from the top thereof.

5. The method of recovering desirable hydrocarbons from an original normally gaseous charge consisting mainly of normally gaseous constituents and containing said desirable hydrocarbons, which consists in subjecting said charge to compression and cooling in a plurality of stages at progressively increasing pressures with separation of condensates from the uncondensed portion of the charge after each stage, collecting and mixing together all of the condensates, introducing the mixed condensates into a rectification zone, also introducing said uncondensed portion of the charge without cooling into the same rectification zone, rectifying said condensates and said uncondensed portion of the charge in said rectification zone into a stabilized fraction containing said desirable hydrocarbons which is withdrawn from the bottom of said zone and withdrawing the remainder of said charge from the top thereof.

6. The method of recovering desirable hydroconsisting mainly of normally gaseous constituents and containing said desirable hydrocarbons which consists in dividing said charge into a gaseous stream and a liquid stream by subjecting said charge to stage compression and cooling at progressively increasing pressures with separation of condensate from the uncondensed portion of the charge between the stages, the finally uncondensed portion of said charge forming said gaseous stream and said condensate forming said liquid stream, introducing said liquid stream into a rectification zone, also introducing said gaseous stream without cooling into said zone, rectifying said streams in said zone into a stabilized fraction containing said desirable hydrocarbons which is withdrawn from the lower portion of said zone and withdrawing the remainder of said charge from the upper portion thereof.

7. The method of recovering desirable hydrocarbons from an original normally gaseous charge consisting mainly of normally gaseous constituents and containing said desirable hydrocarbons which consists in dividing said charge into a gaseous stream and a liquid stream by subjecting said charge to stage compression and cooling at progressively increasing pressures, with separation of condensate from the uncondensed portion of the charge between the stages except the final one, the finally uncondensed portion of said charge forming said gaseous stream and said condensate forming said liquid stream, introducing said liquid stream into a rectification zone, also introducing said gaseous stream directly into said zone, rectifying said streams in said zone into a stabilized fraction containing said desirable hydrocarbons which is withdrawn from the lower portion of said zone and withdrawing the remainder of said charge from the upper portion thereof.

PAUL M. RAIGORODSKY. 

